With the increased interest in utilizing oil, gas and other resources in the arctic regions of the earth, there has developed a need for improved equipment for operating in ice-covered waters. For example, in Patent No. 3,768,428 there is described a marine vessel with rotary type ice-chipping equipment mounted on the bow of the vessel for cutting a channel through the ice. In such an arrangement, rotating cutter blades shear off or chip away fragments of ice from the ice sheet at relatively high speed to form an open channel through the ice sheet.
Studies of the shearing action taking place as the cutter blades are driven through the ice to cut away the chips and larger pieces of ice from the face of the ice sheet indicate that the cutting action involves forming a fracture ahead of the cutting edge, followed by a wedging apart of the ice along the fracture to separate the ice chips from the ice sheet. The separation of the ice along the fracture by the wedging action of the high speed cutter momentarily produces a void into which water or air must move to equalize the pressure with the surrounding ambient condition. Thus a pressure drop exists which tends to resist the separation of the ice particles along the cleavage. It has been found that a substantial amount of energy is dissipated by the cutters in overcoming the result of this partial vacuum effect produced at the moment the cleavage takes place between each particle of ice as it is removed from the ice sheet by the cutters.